An overview is given of the approach followed by the parTool project in developing a parallel programming system. The key feature of parTool is a separation of algorithm specifications and the allocation of hardware resources to data and computations. Algorithms are formulated at an abstract level in a specification language having its own ideal virtual machine, thus preserving the parallelism inherent in the algorithm. Mapping the algorithm onto a specific target machine is done by adding annotations to the description of the algorithm. Porting a program from one machine to another is done by merely changing the mapping annotations. Two high-level specification languages in the parTool system are presented; the parallel transaction-based language Vista, and the data-parallel language Booster.<>